Google’s new Mobile Search tool with voice recognition is coming under fire this week as the application apparently violates the terms of the iPhone SDK. The issue here is the applications use of the proximity sensor. According to the iPhone SDK, the only permitted use of the proximity sensor it to turn the phone’s display off when it is close to the face and back on again when the phone is moved away. The Google mobile app however, uses the proximity sensor to prompt the application to start “listening” while the user begins speaking search queries, as well as delivering audible prompts to your assist with searching. John Gruber and Erica Sadun have accused Google of using private APIs not included in the iPhone SDK in order to deliver this functionality, thereby violating the iPhone’s SDK and giving its application an unfair advantage over other applications that adhere to Apple’s standards. Google chimed in on Wednesday and admitted that its application does indeed violate the terms of the iPhone SDK. Google did not admit to the more serious offense of using private APIs, but it did use undocumented APIs which are not intended for use during the development of applications. D’oh! It is unknown at this point whether Apple will enforce the rules of the iPhone SDK or look the other way. If it does enforce the rules, Google’s latest application could be pulled from the App store and it may be forced to rewrite, at the minimum, the offending portion of the application.